Help. Red drops out, but OSD colors fine

Reaperman · May 29, 2022

I'm looking for some troubleshooting help.

I've got a VGA CRT that loses red (and maybe some green sometimes) periodically. The example in the vid seems like green is low too)

Notes and observations:

Sometimes the colors come back, sometimes not (immediate restart doesn't usually work, but on fully cold start it works)
OSD colors are -fine-. purples are purple, reds are red.
starts dropping out after 30+ minutes. sometimes more like an hour.
I did not spot any individual color pots on the chassis or neckboard, just the flyback knobs (and I played with those without much luck getting red back)
I've jiggled just about every wire in this thing looking for harness problems
I reflowed the connector on the monitor adjust board (since it needed that, and was loose anyway)
One time today it picked the exact moment we slid it against the wall to drop red again--maybe a coincidence
Sometimes the red fades back in over a few minutes, but it always drops all at once.
Frequently there are a few flickers of red dropping (between a few frames and a few seconds) a few minutes before 'the long drop'
After pulling it away from the wall for troubleshooting, it did it after a few hours, and started behaving again for some reason. I then got 4+ hours of good running (checking periodically), but of course it waits until I sit down for ~30 min of gaming and then drops red (~10 min before the video below)

Anybody got an idea what I should check? I'd hate to think the system board, or the 3dfx voodoo card, but maybe.

When it behaves, this screen is actually really pretty.

Edited May 29, 2022 by Reaperman

Reaperman · May 30, 2022

Okay, so it's the next day, and I've run this thing from 1400-2130 without *any* problems and played it for several lengthy periods throughout the day. I don't get this thing. Looked beautiful throughout, which was fun, but kind of hurts troubleshooting. I'd have run it longer, but I share that wall with neighbors that are probably too polite to tell me how much they hate me, and barry leicht.

Something in that cab's probably slowly dying, but I'm wondering if maybe sufficient use prevents it from manifesting. This weekend is the most it's been run since I got it in january, and I only started noticing the issue when I left town on business for a week. Still, my other arcade cab sits neglected and unused for probably a year or more between plays, so it's be great if SF rush didn't demand so much from me. ?

I've also noticed the monitor's digital settings board forgets the 'green' level on poweroff or preset switching (defaulting to 74 of 100 every time), where blue and red get saved, so I rebalanced all the colors/brightness/contrast to 'deal' with green being locked at 74. 'Quirky' personality this thing's picked up over the years.

Edited May 30, 2022 by Reaperman